A bearing unit comprises an outer stationary race (1) with a first inner
passage (6) for the air, and two axially adjacent inner half-races (2a,
2b) rotatable with the hub of a wheel. Formed between the inner half-races
are essentially radial second inner air passages (7, 71, 72). These passages
have surfaces (71d, 72d) inclined forwardly with respect
to a direction of rotation (A, B) so as to favor the air flow through the rotating
part of the bearing.
